Lacking social competence is a primary feature of autism. For those children, interventions to improve social competence are important. Most interventions focusing on social competence have occurred in classroom or clinic settings. Children with autism, however, spend the majority of their time in home and community environments. Siblings in those settings might well be able to support or enhance social communicative development of children with autism. Little research has examined social intervention involving siblings and their brother or sister with autism in a natural environment. Therefore, the purpose of this project is to develop and obtain preliminary evidence of the efficacy of a sibling-mediated intervention designed to improve the social communicational skills of young children with autism spectrum disorder (ASD). The study seeks to answer the following questions (1) does a sibling-mediated social communicative intervention produce changes in social communicative behaviors of young children with ASD? (2) if the intervention produces an increase in overall interactions (e.g., social initiations/responses, social communicative behaviors) between children with ASD and their typically developing siblings, will this increase be maintained for a certain period of time once the intervention has stopped and generalize to a setting outside of home? (3) are the outcomes of the intervention socially valid? A single subject multiple-baseline design will be used with twelve sibling dyads to assess the efficacy of the intervention on the social communicative behaviors of children with ASD. Single subject design (i.e., single case experimental design) is regarded as an appropriate strategy to begin testing an intervention and establishing potential efficacy because this design can "yield evidence that the technique has a clear, replicable effect on a specific behavior (Smith, Scahill, Dawson, Guthrie, Lord, Odom, Rogers, &Wagner, 2007, p. 356)". Both qualitative (i.e., interview) and quantitative (i.e., observations and developmental evaluation on social communication skills) data will be collected and analyzed. This study will extend previous research by conducting the study at home settings (i.e., naturalistic environment), investigating the changes of social behaviors of children with ASD, and documenting the presence or absence of cross-setting generalization of sibling mediated intervention. Most importantly, the results of this study will be used to assemble intervention techniques into a manual and move forward for larger size full implementation and evaluation (e.g., randomized clinical trials). PUBLIC HEALTH RELEVANCE: The purpose of this project is to develop and obtain preliminary evidence of the efficacy of a sibling-mediated intervention designed to improve the social communicational skills of young children with autism spectrum disorder (ASD). The aim is to develop and test the sibling-mediated intervention for young children with confirmed or suspected autism spectrum disorders in terms of social communicative outcomes at home and community settings.